The long-term objective of this project is to contribute to an understanding of the neurobiological bases of the affective disorders of depression and mania. The central idea behind the experiments proposed is that these disorders have behaviorally-described subcomponents, and that these components reflect the activity of anatomically and perhaps chemically distinct parts of the brain. Rather than attempting to create an "animal model" of depression or mania, these experiments are designed to examine brain mechanisms which, in animal tests, appear to reflect processes which in humans are described by terms such as pleasure appreciation, motivation, and cognition. The dysfunctions of these mechanisms in depression are described as anhedonia, psychomotor retardation, and "thinking disorder." These animal experiments rely upon a conceptual scheme developed by the author to assess changes in intracranial self-stimulation following brain manipulations. Specifically brain areas have been identified using the autotitration self-stimulation procedure which seem to control pleasure appreciation and motivation. These studies will further investigate the neural bases of these phenomena and test the ideas developed with the conventional rewards of food and water.